GE MiCOM P145 Agile User Manual

The action of setting the PN> threshold to zer
o would effectively disable the wattmetric function and the device
would operate as a basic, sensitive directional earth fault element. However, if this is required, then the SEF option
can be selected from the SEF/REF Options cell in the menu.
Note:
The residual power setting, PN>, is scaled by the programmed Transformer ratios.
A further point to note is that when a power threshold other than zero is selected, a slight alteration is made to the
angular boundaries of the dir
ectional characteristic. Rather than being ±90° fr
om the RCA, they are made slightly
narrower at ±85°.
The directional check criteria is as follows:
Directional forward: -85° < (angle(IN) - angle(VN + 180°) - RCA) < 85°
Directional reverse: -85° > (angle(IN) - angle(VN + 180°) - RCA) > 85°
11.5.2 ICOS PHI / ISIN PHI CHARACTERISTIC
In some applications, the residual current on the healthy feeder can lie just inside the operating boundary
following a fault condition. The r
esidual curr
ent for the faulted feeder lies close to the operating boundary.
E00618
Reverse
Operation
Reverse
Operation
Forward
Operation
Polarising
Voltage
Healthy
Feeder
Faulted
Feeder
Icos(ϕ2)
Icos(ϕ1)
ϕ1
ϕ2
Figure 63: Operating characteristic for Icos
The diagram illustrates the method of discrimination when the real (cosf
) component is considered. Faults close to
the polarising voltage will have a higher magnitude than those close to the operating boundary. In the diagram,
we assume that the current magnitude I is in both the faulted and non-faulted feeders.
●
For the active component Icos, the criterion for operation is: Icosf > ISEF>(n) current
●
For the reactive component Isin, the criterion for operation is: Isinf > ISEF>(n) current
Where ISEF>(n) current is the sensitive earth fault current setting for the stage in question
If any stage is set to non-directional, the element reverts back to normal operation based on current magnitude I
with no directional decision. In this case, correct discrimination is achieved by means of an Icos characteristic as
the faulted feeder will have a large active component of residual current, whilst the healthy feeder will have a
small value.
Chapter 6 - Current Protection Functions P14x
134 P14xEd1-TM-EN-1

GE MiCOM P145 Agile Specifications

General

Brand	GE
Model	MiCOM P145 Agile
Category	Control Unit
Language	English